In ion beam therapy, a movement of the tumor is particularly challenging for the irradiation to ensure that the clinical target volume is covered with the prescribed dose despite the movement. For this purpose, specifically designed safety margins are typically used in ion beam therapy with a scattered beam, which has hitherto been considered sufficient.
With a scanned beam, however, interference effects will occur that require further measures. These include beam application using so-called gating, or so-called beam tracking, each of which are based on a movement detection system which supplies the tumor movement or a surrogate of the tumor movement, which is used in real time in order to optionally interrupt the beam (gating) or to cause active tracking (beam tracking). The quality of this signal has an influential role since the precision thereof has a direct impact on the precision of the total irradiation. Gating and beam tracking are generally known to those skilled in the art; for gating see e.g. “Respiratory Gated Irradiation System for Heavy-Ion Radiotherapy” by Shinichi Minohara et al. in Int. J. Oncology Biol. Phys., Vol. 47, No. 4, pp. 1097-1103, 2000, or “Gated Irradiation with Scanned Particle Beams” by Christoph Bert et al. in Int. J. Oncology Biol. Phys., Vol. 73, No. 4, pp. 1270-1275, 2009; and for beam tracking e.g. DE 10 2004 028 035 A1, each of which are hereby incorporated by reference.
Various movement detection systems are available on the market. Some movement detection systems measure a so-called movement surrogate, such as the breath temperature, the movement of the abdomen (in 1D, 2D, or 3D), the circumference of the abdomen/thorax, or the flow of breathing air. By contrast, other movement detection systems directly detect the movement of the tumor, for example based on fluoroscopy (with/without implanted radio-opaque markers), radio transponders, or ultrasound. In addition, combinations of these systems are used to combine their advantages, for example sparse fluoroscopy (high quality, but exposure dose for the patient) neuronally linked with an abdominal wall detection system (lower quality, but no exposure dose for the patient).
Movement detection systems for directly detecting the tumor movement often involve surgery in the patient or a significantly higher dose for the patient, for example in conventional X-ray fluoroscopy, especially when using high image acquisition rates. External surrogate-based movement detection systems are inherently limited to perform a very indirect measurement, which is why, among other things, the precision of the detection of the tumor movement needs to be improved. Furthermore, tumor movement may be highly complex, e.g. in case of a lung tumor, and may comprise translational, rotational, and compressive/dilatory components in all dimensions.
Moreover, all of the above systems consider the purely geometrical movement of the target volume, which in ion therapy is exclusively used in conjunction with, e.g., 4D CT datasets, since the range of the beam is influential. In fact, it is not only the spatial movement which is relevant for the precise deposition of the desired dose during irradiation, but rather the effect of the spatial movement on the energy loss of the ion beam, which may depend on other factors, such as the local distribution of tissue density.
Therefore, further improvements to these known methods are desirable, in particular with regard to the precision.
From EP 2 400 506 a device is known which generates at least two different particle beams, the second particle beam thereof being used to detect the movement of the target volume. For this purpose, two ion sources are used to produce ions of different types, which are brought together in a mixing chamber.
However, this method can only be used for certain combinations of ions and depends on the nature of the accelerator device. In addition, certain parameters of the two ion beams can only be influenced jointly. Therefore, the inventors searched for another solution, particularly in terms of complexity, flexibility, and the restrictions imposed by the entanglement of the two ion beams in the approach described in EP 2 400 506.
General Description
The present disclosure is therefore based on the object to provide a method and an irradiation system for irradiating a target volume with an ion beam, which allow high precision irradiation in spite of a moving target volume.
Another aspect of the object of the present disclosure is to provide a method and an irradiation system for irradiating a moving target volume with an ion beam, which enable to determine as accurately as possible the adverse effect of the movement of the target volume on the energy loss and the range of the ion beam in the target volume.
Yet another aspect of the object of the present disclosure is to provide a method and an irradiation system for irradiating a moving target volume with an ion beam, which allow for precise yet flexible movement detection of the target volume and which are independent of the accelerator device and can optionally even be easily retrofitted.
The object of the present disclosure is achieved by the subject matter of the independent claims. Various embodiments of the present disclosure are specified in the dependent claims.
A method is provided for irradiating a target volume that is moving during the irradiation with an ion beam. First, the ion beam is generated by an accelerator device and is accelerated and guided to the target volume. The accelerator device in particular comprises a circular accelerator such as a cyclotron or synchrotron, a linear accelerator, or a combination thereof.
The term ion beam in particular refers to a proton beam or a beam of heavier ions such as, e.g., oxygen or carbon. Such irradiation systems developed by the two applicants are found, e.g., at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, and at the Heidelberg Ion Beam Therapy Center (HIT), where in particular 12C ions are used for irradiation. However, other charged hadronic particle beams, such as pions etc., are not excluded.
According to the present disclosure, the irradiation of the target volume is divided over time into at least one radiography phase and at least one deposition phase, to alter the energy of the ion beam, i.e. one and the same ion beam, as a function of time between the at least one radiography phase and the at least one deposition phase, in a manner so that                i) in the at least one radiography phase, the range of the ion beam is distal with respect to the target volume (behind the target volume as seen in beam direction), so that in the at least one radiography phase the ion beam passes through or screens the target volume to acquire an ion radiograph of the target volume using the ion beam, by detecting the ion beam after it has passed through the target volume using an ion radiography detector arranged distal with respect to the target volume; and        ii) in the at least one deposition phase, the range of the ion beam is within the target volume, so that the ion beam is stopped in the target volume to deposit a predetermined dose in the target volume, namely the dose planned in the irradiation plan.        
Ion radiography allows to detect the movement of the target volume, however, radiography and deposition are accomplished using one and the same ion beam, but with a different energy and consecutively in time. Therefore, in the radiography phase the beam range is adjusted such that the Bragg peak is located distally of the patient, and, more precisely, within the ion radiography detector, to measure the position of the Bragg peak using the energy-resolving and spatially resolving ion radiography detector by stopping the ion beam in the ion radiography detector. For this purpose, therefore, the energy of the ion beam is adjusted to a higher radiography energy in the radiography phase and to a lower deposition energy during the deposition phase. Thus, the alternation between radiography phase and deposition phase comprises an alternation of the energy of the ion beam.
For example, a carbon ion beam is generated which substantially completely passes through the target volume with an energy E′ of about 600 MeV/u and which is used with this energy E′ for radiography, and which is used with a reduced energy E in a range of about 250 MeV/u for dose deposition according to the irradiation plan.
Thus, both the dose deposition and the radiography can be performed with the same ion beam, and it suffice to merely alter or “switch” the energy. In this case, the alteration or switching of the energy of the beam may be effected during irradiation, in particular in real time, for example during a so-called spill in case of a synchrotron-based accelerator device, or in an irradiation pause between spills. The alteration or switching between the deposition energy and the radiography energy must not be confused with the much smaller change in energy for irradiating different isoenergy layers for which the beam range is altered by only a few millimeters and which is optionally performed additionally. Therefore, due to the temporal separation, certain parameters of the deposition and the ion radiography can be adjusted independently, in particular the lateral coverage of the target volume during a scanning process.
Accordingly, the present disclosure enables high-precision movement tracking. Range changes caused by the movement of the target volume can be directly determined from the ion radiographs, without using an error-prone conversion from the x-ray attenuation to the change in particle range. In fact, the ion radiograph “sees” the movement of the target volume in the same manner as during deposition, since the energy loss of the same ion beam is determined. The only difference between deposition and radiography is the energy of the ion beam, which minimizes the differences in the effect of the movement (translatory, rotary, compression/dilatation). In other words, ion radiography measures the same physical effect of the movement of the target volume which also occurs during deposition—except for the difference in ion energy, whose influence may, however, be calculated very accurately. Moreover, a lower dose can be assumed as compared to conventional fluoroscopy.
Moreover, the method can be carried out without major modifications of the accelerator device. Particularly easily, for example, the accelerator device is set to the higher radiography energy, and is then reduced from the higher radiography energy to the lower deposition energy in the deposition phase or phases by decelerating the ion beam using a passive energy modulator. In this manner it is possible to easily vary the energy of the ion beam rapidly enough to alternately irradiate the tumor (deposition) and to perform radiography and to be able to intervene in the irradiation in real time in response to the movement of the target volume for controlling purposes. For example, for this purpose, a digital, e.g. rotating pie-shaped energy modulator proximal with respect to the target volume (in front of the target volume as seen in the beam direction) with one pie segment missing is irradiated in order to modulate the energy and hence the range of the beam between a position in the target volume and a position distal with respect to the patient. In the area of the missing pie segment, the energy of the ion beam remains unchanged (radiography phase), and in the remaining area the energy of the ion beam is reduced to the deposition energy due to deceleration in the material of the modulator. Again, this particularly digital modulator must not to be confused with the known wedge systems for actively adjusting the beam range according to the movement of the target volume in beam tracking, which is optionally provided additionally.
Alternatively, the energy may be altered using binary modulator panels, such as described e.g. in “The PSI Gantry 2: a second generation proton scanning gantry” by Eros Pedroni et al. in Z. Med. Phys. 14 (2004), pp. 25-34, or by varying the settings on the flat-top in case of synchrotron-based acceleration, such as described e.g. in “Update of an Accelerator Control System for the New Treatment Facility at HIMAC” by Y. Iwata et al. in Proceedings of EPAC08, Genoa, Italy, pp. 1800-1802, which are hereby incorporated by reference in this regard. However, it is also possible to use a so-called Cyc-LINAC, such as described e.g. in “High Frequency Linacs for Hadron Therapy” by Ugo Amaldi et al. in Reviews of Accelerator Science and Technology, Vol. 2 (2009), pp. 111-131, which is hereby incorporated by reference in this regard. In the Cyc-LINAC, jumps in range of an order of magnitude as required for the alternation between the radiography energy and deposition energy can be effected by turning off and on individual cavities of the linear accelerator. Thus, the variation in energy may be only effected following the acceleration in the accelerator device (passive modulator), or at the end of acceleration (Cyc-LINAC), at least preferably not before the acceleration.
Accordingly, the ion radiography detector is in particular an energy-resolving detector which measures the (remaining) energy of the ion beam after it has passed through the target volume. Based thereon, the energy loss caused by the passage through the target volume can be calculated, and from this, in turn, the effect of the movement of the target volume on the deposition can be determined.
Thus, one and the same ion beam is in particular used for the deposition and for the ion radiography, in the sense that the ion species and the charge are identical and only the energy is different. That is, one and the same ion beam is used, whose energy is varied consecutively in time, rather than two different ion beams at the same time.
In other words, with the above condition, ion radiography and deposition are performed consecutively in time and independently of one another. In particular, there will be no deposition during the radiography phase and/or no ion radiography during the deposition phase.
According to a preferred embodiment of the present disclosure, the irradiation of the target volume is divided over time into a plurality of radiography phases and a plurality of deposition phases,                wherein between the radiography phases and the deposition phases the energy of the ion beam is alternately switched up and down, so that in alternating cycles:        i) in the radiography phases, the range of the ion beam is distal with respect to the target volume, so that in the radiography phases the ion beam passes through or screens the target volume and ion radiographs of the target volume are acquired by means of the ion beam by detecting the ion beam using an ion radiography detector that is arranged distal with respect to the target volume; and        ii) in the deposition phases, the range of the ion beam is within the target volume, so that the ion beam is stopped in the target volume to deposit a respective predetermined dose in the target volume.        
Furthermore, the timing of the radiography phases may be matched with the movement phases of the target volume. Alternatively or additionally, the timing of the radiography phases may be matched with the extraction phases of the accelerator device (e.g. spills in a synchrotron) and/or with the timing of the irradiation of the isoenergy layers, if the target volume is divided into isoenergy layers that are irradiated successively.
If in the deposition phases different isoenergy layers of the target volume are targeted with the ion beam in order to deposit a respective predetermined dose in the isoenergy layers, for example, a radiography measurement according to i) may be performed at least prior to the irradiation for depositing a dose in each isoenergy layer, and/or an ion radiography measurement is performed at the beginning of each movement phase or each spill.
The intensity of the ion beam may be set to be considerably higher in the at least one or the plurality of deposition phases than in the at least one or the plurality of radiography phases, which may also be controlled in real time. This permits to keep the dose to the patient low.
If the target volume is cyclically moving during irradiation, such as, e.g., a lung tumor while breathing, the cyclic movement of the target volume is divided into a plurality of movement phases. In conjunction with the present disclosure it is helpful if the duration of the at least one radiography phase or the plurality of radiography phases is chosen so as to be not greater than the duration of each of the movement phases. In this case, if desired, a ion radiography measurement may be performed in each movement phase, preferably at the beginning thereof. In other words, steps i) and ii) as defined above are performed in the same movement phase, i.e. the radiography phase and the deposition phase are at least partly in the same movement phase.
Accordingly, this permits to achieve a particularly precise and reliable movement tracking.
The present disclosure is combined with an irradiation with active ion beam tracking to compensate for the movement of the target volume (so-called beam tracking). The active tracking movement of the ion beam, i.e. beam tracking, may be controlled based on the ion radiography measurement performed by the ion radiography detector. This controlling of the active tracking movement of the ion beam (beam tracking) in response to the radiography measurement may as well be performed in real time.
Moreover, due to the temporal separation of the radiography and the deposition, the ion beam can be controlled independently in the radiography phase and in the deposition phase. In particular, in the radiography phase the ion beam can be driven across the lateral extent of the target volume, independently of the deposition.
According to a preferred embodiment of the present disclosure, the ion radiography detector is designed as a spatially resolving detector, so that in the at least one or the plurality of radiography phases a laterally two-dimensionally spatially resolved ion radiograph is acquired, preferably at least of portions of the Internal Target Volume (ITV, according to ICRU 62), by passing through a plurality of grid points of the target volume and determining the range of the ion beam after it has passed through the target volume for each of the grid points in the ion radiograph to create an at least two-dimensional map of the (water equivalent) range of the ion beam. This map of the range of the ion beam can be used, for example, as a monitoring or control information for at least one subsequent deposition phase.
An at least two-dimensional representation of the target volume in the ion radiograph allows a particularly precise and reliable tracking of the movement of the target volume.
When the irradiation method is a scanning method, for example a raster scanning method, the ion beam in form of a so-called pencil beam is scanned across at least a portion of the clinical target volume in the at least one deposition phase or the plurality of deposition phases, and is wobbled across at least a portion of the lateral area of the target volume in the at least one radiography phase or the plurality of radiography phases.
Accordingly, despite of using a fine pencil beam, a lateral two-dimensional ion radiograph can be acquired in this manner. The wobbling for radiography measurement can be performed independently of the scanning during deposition.
Moreover, this allows for a finer pre-calculation of range losses than on a grid point basis, if desired. For the wobbling, for example, during which the beam is moved quickly over a rather large area, more or even all positions can be compared directly, without being limited to nominal grid positions. A finer resolution may, for example, be of the order of the CT voxel size. CT voxel size is, e.g., only about 1 mm, while the spacing of the grid points during the irradiation with the scanning method typically ranges from 2 to 3 mm.
During the scanning process, in the at least one or the plurality of deposition phases, the ion beam is scanned across the Clinical Target Volume (CTV, according to ICRU 50). In the at least one or the plurality of radiography phases, the ion beam may be wobbled across at least a portion of the lateral area of the Internal Target Volume (ITV, according to ICRU 62) beyond the clinical target volume.
By such rapid wobbling, the lateral position of the beam is driven across all areas of the internal target volume (ITV) and thus across the integral extent of the clinical target volume in all its phases of movement. This wobbling across the entire internal target volume may be performed in a time interval between 1 ms and 1000 ms, for example in a range of about 10 ms, 50 ms, 100 ms, or 500 ms, so that a lateral two-dimensional radiograph of the internal target volume can be acquired during this time interval.
In other words, if an area larger than the clinical target volume (CTV) is irradiated in the radiography measurement, especially if at least the internal target volume (ITV) is covered which represents the clinical target volume (CTV) in all states of movement, the entire range of movement of the target volume can be covered.
Furthermore, a range simulation calculation may be performed in order to calculate simulated target values for the range of the ion beam. In this case, during the irradiation in the radiography phase, the actual (water equivalent) range of the ion beam after having passed through the target volume is determined, and the determined actual ranges are compared with the simulated target values.
Moreover, the range simulation calculation is performed for a plurality of grid points and a multi-dimensional map of simulated target values (so-called “range map”) of the range of the ion beam is created. In this case, during the irradiation in the radiography phase, the actual range of the ion beam after having passed through the target volume is determined, again for a plurality of grid points, and based thereon a multi-dimensional ion radiograph with the respective actual ranges of the ion beam is produced, and the ion radiograph is compared with the map of simulated target values.
By precalculating a map of simulated ranges, in particular a so-called digitally reconstructed range map (DRRM), and by respectively comparing the measurement and the simulation calculation, it is possible to match the movement of the target volume with the movement of the ion beam, which, optionally, allows not only to acquire parameters related to the movement and range change, but also to the interference between the two latter, especially the interplay or pattern.
According to a further preferred embodiment of the present disclosure, the movement of the target volume or a movement surrogate is measured using an appropriate internal or external movement measuring system (sometimes referred to as a motion sensor). According to the present disclosure, the measurement results are automatically associated with the ion radiographs acquired by the ion radiography detector, e.g. by an appropriately programmed microcomputer, and the irradiation is controlled based on the associated data.
However, it is also easily possible to control the alternation between the radiography phases and the deposition phases in response to the measurement results of the movement measuring system.
For example, in a combination with the external movement surrogate, the surrogate information is used to determine a movement phase in which it is verified using a radiograph if the clinical target volume (CTV) or individual monitored points of the clinical target volume (CTV) are in the location as planned.
Furthermore, in the at least one or the plurality of radiography phases the target volume may be irradiated from more than one direction, and in this manner a more than two-dimensional ion radiograph (“2.5D detection”) is acquired, at least locally. This is helpful for irradiation sites where more than one beam tube is available. In this case it is possible to acquire radiographs from more than one direction and thus to enable 2.5D detection. Furthermore, an irradiation similar to “RapicArc” is conceivable with a gantry, so that in this case, again, radiographs can be acquired from different directions within the duration of irradiation, and thus a 3D movement plus range can be reconstructed using suitable reconstruction algorithms. This even enables acquisition of a 4D ion CT.
In total, this provides very comprehensive information about the movement of the target volume.
In summary, the collected data should be evaluated with respect to the expectation in real time, for which purpose the methods known from fluoroscopy can be used, i.e., inter alia, a comparison between measurement and digitally reconstructed range map (DRRM) (even in 4D, i.e. one DRRM per movement phase of the 4D CT), or correlation models between radiography and other surrogates or simultaneously acquired fluoroscopy/radiography data are used.
According to a simple aspect of the present disclosure, in response to the acquired ion radiograph, if predetermined threshold values are exceeded, for example when comparing range simulation and energy loss measurement, an interlock signal is generated, by means of which the irradiation is interrupted.
Thus, the present disclosure is in principle not restricted to movement monitoring alone, rather a verification of the acquired DRRMs is possible, so that for example in case of excessive deviations the irradiation can be interrupted and may optionally even be re-planned. In this case the ion radiography detector measures the ion energy, and thus the particle range which is a relevant factor for the dose is directly detected (in contrast to methods which only detect equivalent values).
Depending on the contrast in the irradiated anatomical region, it is also possible to implant markers (gold spheres, carbon spheres, etc.) to define visible points in the ion radiograph. The present disclosure is furthermore also applicable to irradiation with inter-fractionary movement or to static head-and-neck irradiation, for example to enable positioning or to provide an interlock signal in the event that nevertheless unexpected movements do occur.
The present disclosure also provides an irradiation system for irradiating a moving target volume with an ion beam, which permits to perform the method described above. For this purpose, the irradiation system comprises:                an accelerator and beam guiding device for generating and accelerating an ion beam and for guiding and directing the ion beam onto the target volume;        a controller device for controlling the irradiation system;        a device for varying the energy of the ion beam over time during the irradiation or in an irradiation pause, between at least one radiography phase and at least one deposition phase, especially in addition to the alteration in range for dose deposition in different isoenergy layers, which device is adapted                    i) in the at least one radiography phase, to adjust the energy of the ion beam to a higher radiography energy, with a range distal with respect to the target volume or distal to the patient (behind, as seen in the beam direction), more precisely within the ion radiography detector, so that the ion beam passes through or screens the target volume;            ii) in the at least one deposition phase, to adjust the energy of the ion beam to a lower deposition energy, with a range in the target volume and so that the ion beam is stopped in the target volume to deposit the planned dose in the target volume; and                        an ion radiography detector arranged distal with respect to the target volume for acquiring ion radiographs of the target volume by stopping and detecting the ion beam that has passed through the target volume in the ion radiography detector during the radiography phase.        
The means for varying the energy of the ion beam over time may alternately switch up and down the energy of the ion beam between the radiography energy and the deposition energy in a cyclic sequence that includes a plurality of radiography phases and a plurality of deposition phases, in particular during the irradiation or in an irradiation pause, and in addition to the alteration of range for targeting the isoenergy layers in the deposition phase.
The ion radiography detector in particular has a temporal resolution sufficient to produce a new radiograph in each radiography phase, in order to be capable to optionally control the irradiation in real time.
The controller device may control the irradiation system in a manner so that in the deposition phases different isoenergy layers of the target volume are targeted with the ion beam to deposit a respective predetermined dose in each of the isoenergy layers, and so that at least before the irradiation for dose deposition in each isoenergy layer a radiography measurement is performed using the ion radiography detector.
A passive energy modulator may be used, and in this case the ion beam is first generated by the accelerator device with the radiography energy, and in the deposition phase the energy of the ion beam is reduced to the deposition energy by deceleration in the material of the energy modulator. The passive energy modulator may, for example, be a round plate having a pie-segment-shaped cutout and is rotating in the ion beam, so that in cyclically alternating periods the ion beam passes through the material of the plate and is thereby decelerated to the deposition energy (deposition phase) or passes unattenuated through the pie-segment-shaped cutout (radiography phase).
Furthermore, the controller device may control the irradiation system such that during deposition in the target volume the intensity of the ion beam is higher than during the radiography measurement, to keep the additional radiation exposure caused by the radiography measurement low for the patient.
In preparation of the irradiation, a microcomputer may divide the movement of a cyclically moving target volume, e.g. due to breathing, into several movement phases. When a pie-shaped energy modulator is used, the shape and rotational speed thereof may be adapted to the duration of the movement phases in a manner so that the duration of the radiography phases is shorter than the duration of the movement phases.
If means for active ion beam tracking are provided to compensate for the movement of the target volume (beam tracking), the controller device may be operatively connected therewith for controlling the beam tracking process in response to the ion radiographs acquired using the ion radiography detector.
The ion radiography detector may include an energy resolving and spatially resolving detector which acquires an energy resolved and laterally two-dimensionally spatially resolved ion radiograph in each case, at least of portions of the internal target volume (ITV). A computing means then determines the range of the ion beam after it has passed through the target volume for each of the grid points and creates a two-dimensional map of the range of the ion beam after having passed through the target volume.
The scanning device that may be provided for scanning the ion pencil beam (diameter of typically a few millimeters) is controlled by the controller device in a manner so that for dose deposition the ion beam is scanned across the target volume in two or three dimensions, and so that for radiography the ion beam is wobbled across at least a portion of the lateral area of the target volume, independently of the scanning for deposition purposes because consecutively in time. The same scanning magnets may be used for the scanning and the wobbling, but it is as well possible to install separate magnets for the wobbling process, for example in case the scanning magnets are not fast enough for wobbling.
For example, the controller device controls the scanning device (with or without separate wobbling magnets) so that during dose deposition the ion beam is scanned across the clinical target volume (CTV, ICRU 50), and during radiographing it is wobbled across a greater lateral area than the clinical target volume, in particular across the internal target volume (ITV, ICRU 62).
The range simulation calculation described above is typically performed by a suitably programmed microcomputer which also performs the comparison with the determined actual ranges and then generates control signals, preferably in real time, which are used, for example, to adapt or interrupt the irradiation. The same applies to the embodiment in which the actually measured multi-dimensional radiographs are compared with the map of simulated target values.
In particular, the controller device receives the measurement results of the movement measuring system and the ion radiographs of the ion radiography detector to automatically associate the measurement results and the ion radiographs, and then controls the irradiation in response to these associated data.
Alternatively, the controller device controls the alternation between the radiography phases and the deposition phases in response to the measurement results of the movement measuring system.
Moreover, the irradiation system may include a plurality of beam tubes and/or a rotatable gantry, by means of which the target volume can be irradiated from more than one direction to acquire a locally more than two-dimensional ion radiograph.
The method and the irradiation system of the present disclosure are in particular adapted for tumor therapy. However, they may also be used to irradiate a target volume which does not belong to a human or animal body. For example, a phantom which, by way of example, includes a target volume for movement simulation, may be irradiated.
The present disclosure will now be described in more detail by way of exemplary embodiments and with reference to the figures, in which identical and similar elements are partly designated with the same reference numerals, and wherein the features of the various exemplary embodiments can be combined.